Field of the Invention
The present invention relates to an imaging apparatus, an imaging system, and a signal processing method.
Background
An image pickup element has pixels on its element surface, and each of the pixels has a color filter (hereinafter, called a CF) allowing a specific wavelength component such as light of colors red, green, and blue to pass through. Hereinafter, red, green, and blue will be called R, G, and B, respectively. A pixel having a CF for R, a pixel having a CF for G, and a pixel having a CF for B will be called, a red pixel, a green pixel, and a blue pixel, respectively, hereinafter. The red pixel, green pixel, and blue pixel will collectively be called RGB pixels.
For improved sensitivity of image pickup elements, configurations for increasing the proportion of pixels allowing easy acquisition of information regarding brightness have been proposed. Among such pixels, use of a white pixel (hereinafter, called a W pixel) which widely transmits light of a visible light region can improve the sensitivity so that an image having a high S/N ratio can be acquired.
Japanese Patent Laid-Open No. 2014-072658 discloses that interpolation processing is performed on an output signal from an image pickup element having an RGBW pattern including RGB pixels and a W pixel.
According to Japanese Patent Laid-Open No. 2014-072658, pixels in neighborhood of a pixel of interest are used to obtain correlations in a plurality of directions. It is disclosed therein that the correlations in different directions are used as a criterion for determining an interpolation method for the pixel of interest. Japanese Patent Laid-Open No. 2014-072658 further discloses that pixel data of pixels of one color having a pixel of a different color therebetween or pixel data of adjacent pixels of different colors are used.